Orthoester stabilized polyvinyl chloride resins

ABSTRACT

Vinyl chloride resins are stabilized with orthoesters derived by the condensation of lower alkyl substituted orthoesters with polyhydric alcohols such as glycerol, sorbitol, mannitol, 1,2,4 butane triol, and 1,2,6 hexane triol.

United States Patent Wood 1 Feb. 22, 1972 [54] ORTHOESTER STABILIZED [51] Int. Cl. ..C08t 45/58 POLYVINYL CHLORIDE RESINS [58] Field of Search ..260/45.80, 45.8 A

[72] Inventor: Louis L. Wood, 11715 Smoketree Road, 5 R f n Cied Potomac, Md. 20854 Fned: Jan. 30, 1970 UNITED STATES PATENTS 2,789,101 4 1957 W'l ..260 45.85 X 211 Appl. No.: 7,258 I Primary ExaminerDonald E. Czaja Related Apphcauon Data Assistant Examiner-M. J Welsh [63] Continuation-impart of Ser. No. 736,256, June 12, tt ney-Elt0n Fisher and Kenneth E. Prince 1968, abandoned, which is a continuation-in-part of Ser. N0. 612,066, Dec. 14, 1966, abandoned, which is ABSTRACT a 9 Vinyl chloride resins are stabilized with orthoesters derived by 1965' abandoned whch a commuauon'm'pan of the condensation of lower alkyl substituted orthoesters with 403353 1964 abandonedpolyhydric alcohols such as glycerol, sorbitol, mannitol, 1,2,4

butane triol, and 1,2,6 hexane trial. [52] US. Cl ..260/45.8 A, 260/23 XA, 260/30.6 R,

9 Claims, No Drawings ORTIIOES'IER STABILIZED POLYVINYL CHLORIDE RESINS A thermally present application is a continuation-in-part of my earlier filed application 736,256, filed June 12, 1968 now abandoned, which is a continuation-in-part of 612,066, filed Dec. 14, 1966, now abandoned, which in turn is a continuation-impart of application 499,083, filed Oct. 20, 1965, now abandoned, which in turn is a continuation-in-part of my application 403,353, filed Oct. 13, 1964, now abandoned.

The present invention relates to the stabilization of resins, and more specifically to a novel stabilization agent for stabilizing vinyl chloride polymers and copolymers against the degradation effects of elevated temperatures.

It is well known that vinyl chloride containing resins degrade at elevated temperatures. When vinyl chloride polymers and copolymers are subjected to molding temperatures in excess of about 150 C., they tend to discolor. Serious discoloration occurs even in the relative short period of time required for a molding operation.

To date, numerous stabilizers have been suggested for use in vinyl-chloride-type resins. The most satisfactory of these stabilizers comprise. tin, lead and cadmium containing compounds. These compounds, while performing satisfactorily where toxicity is not a problem, cannot be used where the treated polymer is to come into contact with foodstuffs and the like.

As of the present, a highly effective polyvinyl chloride stabilizer which does not possess toxic characteristics or propensities has not been developed.

It is therefore an object of the present invention to provide a novel class of polyvinyl chloride stabilizers.

It is another object to provide novel stabilizers for polyvinyl chloride containing resins which substantially enhance thermal stability of said resins.

It is a further object to provide a class of polyvinyl chloride stabilizers which are nontoxic and may be used in resins which are used in the packaging of foodstuff materials.

These and still further objects of the present invention will become readily apparent to one skilled in the art from the following detailed description and specific examples.

Broadly, my present invention contemplates the following as polyvinyl chloride stabilizer compounds:

wherein R is hydrogen, phenyl or lower alkyl having one to four carbon atoms; R is lower alkyl having one to four carbon atoms; and n has a value of l to 10.

ll. Complex condensates of lower alkyl substituted ortho esters with multifunctional alcohols such as sorbitol, and mannitol which possess four or more hydroxyl groups per molecule. A typical condensation may be described as follows:

wherein R and R have meanings given above, and R represents the organic residue of a polyfunctional alcohol having a valence ofequal to or greater than 4.

Reaction conditions for forming the present orthoester complex condensates l and II involve reacting from about 0.3 to 3.0, preferably about 0.5 to 2.0 moles of polyhydric alcohol per mole of lower alkyl substituted orthoester at a temperature of from about 50 to 200 C., for from about 0.1 to 72 hours.

The rate and degree of reaction is readily followed by collecting displaced alkanol and comparing to the theoretical amount formed on reaction. The reaction follows conventional chemical kinetics in that an increase in temperature will increase the reaction rate and thus decrease the time duration of reaction. The rate of reaction is economically efficient down to 70 C. to C., with the exchange reaction operable down to about 50 C. The upper range of reaction temperature is governed by reactant and reaction control. Reaction can be effectively controlled at temperatures up to about 200 C. In general, the time duration of heating will be dependent on the temperature at which the reaction is conducted.

The type of orthoesters useful in the practice of the present invention are generally described in U.S. application Ser. No. 574,259, filed Aug. 22, 1966, now abandoned. These compounds are prepared by an ester exchange reaction described by Mkhitaryan, V. J. Gen. Chem., (USSR) 8 1361 (1938). During the exchange reaction, alkoxy groups of readily available lower alkyl substituted orthoesters such as trimethylorthoformate, triethylorthoformate, tripropylorthoformate, tributylorthoformate, trimethylorthoacetate, triethylorthoacetate, tripropylorthoacetate, tributylorthoacetate, trimethylorthopropionate, triethylorthopropionate, tripropylorthopropionate and tributylorthopropionate are displaced by a higher boiling polyhydric alcohol such as glycerol, mannitol, sorbitol, 1,2,4 butane triol, and 1,2,6 hexane triol, producing the orthoester complex condensate and alkanol (alkyl alcohol). Present also may be small amounts of unreacted polyhydric alcohol.

The effectiveness of the present orthoester stabilizers may be enhanced by adding thereto a polyhydric alcohol, preferably from about 0.1 to about 10 moles of a high boiling alcohol per mole of orthoester.

Typical alcohols which may be added possess the general structure wherein R is an organic radical and x has a value of from 1 to 6. Preferably, these alcohols have a boiling point in excess of about C.

1n the above formula, R may be alkyl, alkylphenyl, phenylalkyl, alkylene, phenylene, polyalkoxyalkylene and trivalent counterparts thereof. Typical polyhydric alcohols useful in the practice of the present invention are 0, m, p-xylene, a, a-diol,

trimethylolpropane monopropyl ether, trimethylolpropane monoallyl ether, propylene glycol, diethylene glycol, dimethyloctadiynediol, pentaerythritol, trimethylolpropane, neopentylglycol, benzylalcohol, cetyl alcohol, dipentaerythritol glycerol, mannitol, sorbitol, 1,2,4 butane triol, and 1,2,6 butane triol. When the polyhydric alcohol to be added is the same as that utilized in the ester exchange reaction to produce the orthoester complex condensate, any excess present on completion of reaction need not be removed.

More specifically, I have found that if from about 1 percent to about 10 percent by weight of the above compounds containing orthoester groupings are admixed with polyvinyl chloride, the orthoester compound will stabilize the polyvinyl chloride towards heat induced degration. Furthermore, this stabilization effect may be enhanced by the addition of polyhydric alcohols.

Polyvinyl chlorides which are treated in accordance with the practice of my present invention are those vinyl chloride polymers and vinyl chloride copolymers having a number average molecular weight from about 10,000 to about 150,000 and a weight average molecular weight of from about 20,000 to 1,000.000. These vinyl chloride polymers and copolymers are well known to those skilled in the art and comprise vinyl chloride homopolymers, as well as vinyl chloride copolymers which are prepared by copolymerizing vinyl chloride with a copolymerizable monomer such as unsaturated esters which include vinyl acetate, vinyl formate, vinyl benzoate, vinyl stearate, vinyl oleate, as well as diethyl maleate and diethyl formate. Copolymers may also be prepared by copolymerizing vinyl chloride with an acrylic ester such as methyl-, ethyl-, butyland octyl acrylate. It is also orthoesters, the following specific exanlils contemplated that the vinyl chloride copolymers may be Prepared by polymerizivgxinyl l e??? wi h 4914491 5 wherein n has a value of 1 to 10, with a value of 3 to 4- ji fiFil llji Pfiu.

Ortho- IR Viscosity ester OH (3,400 at 25 content emr centipoise Percent yleld (percent CH (2,900 (Brook- Run Method of preparation and color of theory) 0111.") field) 1 0.li1rnoles1(1;EOA plus 0.75 moles glycerol at 110 to 120 C. for 5-6 79.0, colorless. 83. 5 1. 871 9, 940

ours. a m. 2 50 moles glycerol added over 3 hours to 60 moles TEOA at 130 C. 92.0, orange- 67. 1. 236 28, 250

and 1 atm. Heated 3 more hours at 130l80 C. and 1 atm. 3 1.0 mole glycerol added over 3 hours to 1.0 mole TEOA at 130 to 100, colorless. 68. 1. 054 12, 440

140 C. and 1 atm. Last 25% EtOH removed at to 1 mm. 4 1.0mole 'IEOA and 1.0 mol glycerol plus 0.004moles cetyl alcohol 96.0, colorless 72. 0 0. 985 12, 200

at 130 to 140 C. for 5-0 hours. hazy 5 1.0 mole 'IEOA added to 1.0 mole glycerol plus toluene over 3-4 100, colorless 78. 2 0. 461 45,500

hours at 120 C. EtOH distilled over with toluene. 6 1.05 moles 'IEOA added over 2 hours to 1.0 mole glycerol at 100 to do 83. 4 0. 686 73, 000

110 0. Final EtOH removed at 90-100 at 10 to 1 mm. 7 .5 moles TEOA added over 4-5 hours to 1 mole glycerol at 100l10 61.0, colorless 65. 4 1.127 11, 500

C. plus 1 atm. Final 25% EtOH removed over 4 hours at 90 C. 100 C. and 10 to 1 mm. 8 26.2 moles TOEA added over 4-5 hours to 25.0 moles glycerol plus 100, colorless. 76. 5 0. 843 18,000

0.1 mole cetyl alcohol at 90 to 100 C. and 1 atm. Final 25% EtOH removed over 3 hrs. at 90-100 C. and 10 to 1 mm.

chloride. The above-mentioned copolymers may contain froml EXAMPLE H 0 to 20, and even 40 percent by weight of copolymerizable monomer.

The stabilization agents, namely the orthoesters contem 25 plated herein, are incorporated with the vinyl chloride polymer and copolymers by any conventional means. The blending may be conveniently carried out, first preparing a slurry of finely divided polymer in a solvent for the orthoester such as methanol, acetone, ethyl ether. The solution is then.

separated from the slurry, and the polymer particles are dried. This results in polymer particles which are thoroughly coated; with the orthoesters set forth herein. It is also contemplatedl that the blending may be achieved by milling the polymer at;

the softening temperatures therefor until an intimate blend of the stabilization agent with the polymer. 7 g N w The stabilized vinyl chloride polymers and copolymers contemplated herein may be used in the formation of rigid polyvi-' nyl chloride molded articles. These rigid molded pieces are; formed in extrusion and injection molding devices which are; well known to those skilled in the art and which operate in the neighborhood of 150 to 200 C. The stabilization agents contemplated herein effectively stabilize the vinyl chloride polymer and copolymer during the molding process and make it possible to produce rigid moldings having a low degree of color change and good clarity.

It is also contemplated that the polyvinyl chloride resins stabilized by the present stabilizers may be admixed with various plasticizers such as high boiling esters including the alkyl phthalates, phosphates, adipates, sebacates, azelates, and various polymeric-type ester plasticizers. Also, the present composition may contain other additives such as Zn, Mg, Sn and Ca salts of carboxylic acids, and phosphate esters. Further more, the resins may be included in plastisol-type preparations which are fabricated by dipping and deposit-type molding techniques.

Having described the basic aspects of my present invention, wherein numerals are used as indicated to indicate the "amoral 1m trate embodiments thereof:

EXAMPLEI Poly(glyceryl orthoacetate)-Xll The following table lists reactions of glycerol (95-96 per-- cent. 3-4 percent water) with triethyl orthoacetate (TEOA). In all cases, 90-100 percent of the required amount of ethanol was distilled during the reaction. in several reactions, the addition of a small amount of a monofunctional alcohol (cetyl alcohol) was added as a chain stopper" to keep the molecular weight (viscosity) of the product at a more manageable level. The structure of the compound corresponds to the following:

(XII) OCH2 Poly(glycery1 orthopropionate )XXXI A mixture of 176.3 g. (1 mole) of triethyl orthopropionate and 92 g. (1 mole) of glycerol was heated between to 1 10 C., and ethanol distilled off through a fractionating column (to prevent the loss of unreacted triethyl orthopropionate) at one atmosphere for several hours. Ninety-one grams (1.98 moles) of ethanol were recovered. The liquid pot residue was then processed in a rotary film evaporator at C. and 2 mm. pressure for six hours to give 36 g. (0.785 moles) of ethanol (dry ice trap) and 132.4 g. of po1y(g1yceryl orthopropionate) a colorless syrup having a viscosity of 1835 cps. at 25 C. andan orthoester content of 7.61 meq./g. 98.9 percent of theory). The IR and NMR agree with the structure XXXI below, and a value of 0.3 for the ratio of OH end groups to CH CH C group via the NMR indicates the value of n in structure XXX] is predominantly between 3 and 4.

CH3CH2 H-CHz EXAMPLE Ill Poly( glycerol orthoformate)XXVlll EXAMPLE 1V Poly(sorbityl orthoacetate)-XX1X A slurry of 324 g. of triethyl orthoacetate and 182 g. of sorbitol hemihydrate were heated with stirring at 50 to 1 10 C. for 5 hours at 80 to 110 C. under a vacuum of mm. Hg until distillation of material ceased. A total of 273 g. of ethanol (99 percent of theory) was recovered. The remaining 238 g. of warm thick pale yellow liquid solidified to a glass upon cooling to 25 C.

EXAMPLE V Poly(mannityl orthoacetate)XXX A slurry of 324 g. of triethyl orthoacetate and 182 g. of mannitol were reacted by the procedure set forth in Example IV. A total of 285 g. of ethanol was recovered by distillation. The product weighed 210 g. and was a yellow solid at room 5 6 temperature. tion as in claim 1 wherein said polyhydric alcohol is selected from the group consisting of glycerol, mannitol and sorbitol, EXAMPLE VI and said orthoester is selected from the group consisting of in the following runs, particulate polyvinyl chloride having a y orthoformate methyl Orthoformale, number average molecular weight of about 38,000 was dry 5 tripropyloflhoformatev tl'lbutylol'thoformfltev blended with various amounts of orthoester and/or polyhydric trimethylol'lhoacetate, "ielhylol'thoacemtev alcohol. These samples were then placed in the mixing "imethylorthopropionater trieihylonhopmpionate, chamber of a Brabender Plastograph at 190 C. and open to tripropylorthopropionate and y p p the air. A roller speed of 60 r.p.m. was used to knead the A thermally Stabilized Polyvinyl chloride resin P$ polymer formulations. The Brabender Plastograph conflnu- 10 11011 as in claim 1 wherein said composition contains from ously records the torque required to knead the mass. From the about 1 to 10 P by weight ofsaid P ytorque values, one can determine: 4. Athermally stabilized polyvinyl chloride composition as a. The time required for the powder mixture to fuse into a in Claim 1 whi h n ins from about i to 10 percent by w rkable l stic ma (flux time) weight of an alcohol having a boiling point in excess of about b. The force required to work the plastic mass (average 1 175 C., and having the formula R(OH)x, wherein R is an ortorque value) ganic radical and x has a value of from i to 6.

c. The onset ofcross-linking (decomposition time). 5. A thermally stabilized polyvinyl chloride composition as The actual temperature of the plastic mass was also continuin claim 3 wherein said poly-orthoester is poly(glyceryl ously measured. Small samples of the polymers were also orthoacetate). removed periodically from the mixing chamber and their color 20 6. A thermally stabilized polyvinyl chloride composition as compared to those of the standard Gardner scale. in claim 3 wherein said poly-orthoester is poly(glyceryl TABLE Decomposition Concentime Color (Gardner scale.) tration Flux after Polymer =colorless, 15=brown (parts time, flux (tempera- Stabilizer (numerals refer per hunmln- (min- Torque, ture), 2 4 10 15 Run orthoester described previously) dred) utes utes) kg. degrees m. m. m. m.

1 None 3.0 4.5 1.85 201-212 8 15 5.0 0. 7 15 1. 1-1. 8 170-200 2. 2 2. 2 2. 2 2. 5:8} 2.5 1.1-1.8 100-200 1.2 1.2 1.2 1.8 2.8 0 9-10 1. 8-2. 1 180-218 6. 0 10 12 gig} 0 14 1. 8 2.4 190-212 2.0 2.5 5 2:18 0 5.5 1. 8-2.4 102-200 2.0 0.5 XII 5Z3 7 Cetyl alcohol. 2. 0 0 15. 5 1. 4-2. 4 190-210 2. 0 2. 0 2. 0 3. 0 Stearic aeid 8 I 0 7. 5 1.7-2. 4 190-214 7.5 7.5 9 Cetyl alcohol. 0 6. 5 1.9-2.1 192-210 15 black XXXI 5.0 10 -.{Stearic acid l. 0.5 0 11. 7 194-216 0 0 1. 5

Tn (nonylphenyl) phosphate 0. 3 Acryloid K 120 N 5. 0

Black at 7.5 m.

What is claimed is: orthoformate).

l. A thermally stabilized polyvinyl chloride resin composi- I 7. A thermally stabilized polyvinyl chloride composition as tion comprising polyvinyl chloride and a poly-orthoester in claim 3 wherein said poly-orthoester is poly(glyceryl selected from the group consisting of poly(sorbityl orthopropionate). orthoacetate), poly(mannityl orthoacetate), poly(glyceryl 8. A thermally stabilized polyvinyl chloride composition as orthoformate), poly(glyceryl orthoacetate) and poly(glyceryl in claim 3 wherein said poly-orthoester is poly(sorbityl orthopropionate) produced by the process comprising reactorthoacetate)- ing from about 0.3 to 3.0 moles of polyhydric alcohol per mole A thel'mally Stabilized P y y Chloride composition as of lower alkyl substituted orthoester at a temperature of from in Claim 3 wherein Said poly'orthoester is poly(mannityl about 50 to 200 C. for about 0.1 to about 72 hours. orthoacetate)- 2. A thermally stabilized polyvinyl chloride resin composi- 

2. A thermally stabilized polyvinyl chloride resin composition as in claim 1 wherein said polyhydric alcohol is selected from the group consisting of glycerol, Mannitol and sorbitol, and said orthoester is selected from the group consisting of trimethyl orthoformate, triethyl orthoformate, tripropylorthoformate, tributylorthoformate, trimethylorthoacetate, triethylorthoacetate, trimethylorthopropionate, triethylorthopropionate, tripropylorthopropionate and tributylorthopropionate.
 3. A thermally stabilized polyvinyl chloride resin composition as in claim 1 wherein said composition contains from about 1 to 10 percent by weight of said poly-orthoester.
 4. Athermally stabilized polyvinyl chloride composition as in claim 1 which contains from about 1 to 10 percent by weight of an alcohol having a boiling point in excess of about 175* C., and having the formula R(OH)x, wherein R is an organic radical and x has a value of from 1 to
 6. 5. A thermally stabilized polyvinyl chloride composition as in claim 3 wherein said poly-orthoester is poly(glyceryl orthoacetate).
 6. A thermally stabilized polyvinyl chloride composition as in claim 3 wherein said poly-orthoester is poly(glyceryl orthoformate).
 7. A thermally stabilized polyvinyl chloride composition as in claim 3 wherein said poly-orthoester is poly(glyceryl orthopropionate).
 8. A thermally stabilized polyvinyl chloride composition as in claim 3 wherein said poly-orthoester is poly(sorbityl orthoacetate).
 9. A thermally stabilized polyvinyl chloride composition as in claim 3 wherein said poly-orthoester is poly(mannityl orthoacetate). 